1. Field of the Invention
The present invention relates to an image forming apparatus that forms an image on a long flexible recording medium.
2. Description of the Related Art
Among commonly used image forming apparatus, there are exposure apparatus, such as scanning type printed board exposure apparatus, laser photoplotters and laser printers, that form a desired image on a recording medium by scanning the recording medium with a light beam.
In such exposure apparatus, in the case of a printed board exposure apparatus, for example, image forming is conducted by scanning, with laser light, a board material for a printed wiring board that is a recording medium. The board material for the printed wiring board used here is made by forming a thin film conductor on an insulating layer and covering the thin film conductor with a photoresist.
The printed board exposure apparatus exposes a desired board pattern on the photoresist layer by scanning the board material with laser light modulated on the basis of image data.
The exposed board material for the printed wiring board is removed from the printed board exposure apparatus and photo-etched, whereby a printed board is completed.
In conventional printed board exposure apparatus used in this manner, a long, band-like recording medium in a sheet roll is stretched between a loader, which feeds the recording medium, and an unloader, which collects the recording medium. The stretched portion of the recording medium is placed and fixed on an image forming surface of an image forming table by fixing means (a mechanism), and the image forming table is configured to be slidable with high precision by sliding means (a mechanism). A scanning optical system that scans the recording medium with laser light is disposed directly above the recording medium stretched between the loader and the unloader.
The image forming table, on whose image forming surface the stretched portion of the recording medium is fixed by the fixing means, is conveyed with high precision by the sliding means. As the recording medium is slid with high precision together with the image forming table, the scanning optical system scans the recording medium with laser light modulated on the basis of image data, whereby image forming is conducted.
In such conventional printed board exposure apparatus, image forming is again started after the first image forming ends. Thus, the fixing means of the image forming table is released, the recording medium is fixed by a clamp roller pair of the loader and by a drive roller pair of the unloader so that the recording medium stretched between the loader and the unloader becomes immovable, and the image forming table is moved towards the loader by the sliding means. Next, the recording medium is fixed on the image forming surface of the image forming table by the fixing means of the image forming table. Next, the clamp roller pair of the loader is opened and the recording medium is reeled out by a reel roller pair of the loader to form slack. Next, the image forming table is moved towards the unloader by the sliding means, the recording medium fixed on the image forming surface of the image forming table is scanned by the scanning optical system, the recording medium is collected inside the unloader by the drive roller pair of the unloader, and the next image forming ends. When the next image forming is to be conducted, the above operation is repeated the necessary number of times (e.g., see Japanese Patent Application Laid-Open Publication (JP-A) No. 2000-235267).
In such conventional printed board exposure apparatus, from when image forming ends to until the next image forming starts, the next image forming operation cannot begin until the operation of releasing the fixing means of the image forming table, fixing the recording medium with the loader and the unloader, moving the image forming table towards the loader with the sliding means, fixing the recording medium on the image forming surface of the image forming table with the fixing means of the image forming table, releasing the clamp roller pair of the loader, and reeling out the recording medium with the reel roller pair of the loader to form slack ends. For this reason, there may be a lot of waiting time outside the time in which exposure processing is being conducted.